THE BRAIN HABITBRIDGING THE CONSCIOUS AND UNCONSCIOUS MIND
Mary ET Boyle, Ph. D.
Department of Cognitive Science
UCSD
ETPart 2
How did I get here? What did I do? Start driving
home after work
Aware when you left
Mind started wandering and thinking about other
things
Suddenly you are at home
No memory of the drive
On auto‐pilot!Once you have learned something so well, you stop paying attention to it and thinking about it.
• Slowly acquired associations between stimuli and response
• Trial and error learning• Performance based
Habit memory
•Operates outside of awareness• Trial and error learning• Ridged organization
Dependent on Basal ganglia
Linking thought and movement simultaneously!
Basal ganglia
Forebrain
Midbrain and Brainstem
Image from Mayo Clinic
Largest subcortical brain structure
The basal ganglia receive inputs from the neocortex and, by way of their output nuclei, the basal ganglia nuclei project massively to thalamic nuclei, which in turn project to the frontal cortex. This anatomy means the basal ganglia are in a prime position to influence the executive functions of the forebrain, such as planning for movement and even cognitive behaviors.”
“
Graybiel, Ann. (2000). "The Basal Ganglia." Current Biology, 10(14), R509‐511
Prefrontal cortex
Pre‐motor cortex
M1
Parietal Lobe
caudate
(i)(e)
thalamus
Operational definition of habit:• Behaviors are goal directed get food reward!• Behaviors have not become automaticInitial stage
• Regularly performed behaviors on cue• Cued response – even with lower or no rewardExtended training
• “Behaviors performed not in relation to a current or future goal but rather in relation to a (successful) previous goal.”
Context triggered behavior
forming a habit
repetitive, sequential, context‐triggered
behaviors
Jog, M. S. et al (1999) SCIENCE VOL 286
Memories for habits and skills (implicit or procedural memory) and memories for facts (explicit or episodic memory) are built up in different brain systems and are vulnerable to different neurodegenerative disorders in humans. So that the striatum‐based mechanisms underlying habit formation could be studied, chronic recordings from ensembles of striatal neurons were made with multiple electrodes as rats learned a T‐maze procedural task. Large and widely distributed changes in the neuronal activity patterns occurred in the sensorimotor striatum during behavioral acquisition, culminating in task‐related activity emphasizing the beginning and end of the automatized procedure. The new ensemble patterns remained stable during weeks of subsequent performance of the same task. These results suggest that the encoding of action in the sensorimotor striatum undergoes dynamic reorganization as habit learning proceeds.
Animals with injured basal ganglia developed problems
with tasks such as learning how to run through mazes.
What are the chances of f inding chocolate here???
Yum!
Rat would wander
Sniffing corners
Scratching walls
Could not figure out how to find the chocolate at first.Jog, M. S. et al (1999) SCIENCE VOL 286
While the animal wandered through the maze – the basal ganglia
was firing furiously. When the rat sniffed or
scratched a wall the brain exploded with activity.
Jog, M. S. et al (1999) SCIENCE VOL 286
The experiment was repeated hundreds of times
• Rat’s brain activity changed.
• Rat stopped sniffing corners and making wrong turns.
• Zipped through the maze much faster.
Jog, M. S. et al (1999) SCIENCE VOL 286
Experimental paradigm for assessing habit learning.
Event‐related neuronal firing patterns were recorded in relation to start, tone, turn, and goal reaching from electrodes placed in the sensorimotor striatum (dorsolateral caudo‐putamen).
Reorganization of neuronal activity in the sensorimotor striatum during habit learning.
Schematic activity maps representing the average proportion of task‐related units responsive to different parts of the task from early to late in training.
Jog, M. S. et al (1999) SCIENCE VOL 286
Restructuring striatal neural response
during habit formation
Activity became centered around the
beginning and end of the task
Dopamine neurons shifted
their firing pattern to respond to the earliest indicator
of reward
Dopamine –containing
neurons fired predictively.
striatum
caudate
putamen
• Receives the most input from the cortex
Associated with habits
• Automatic habit response
Decision to perform an action
• Receives (DA) input from substantia nigra (pc)Dopamine input
• Global Pallidus (i/e)Output
How is the template developed?
Gradual tuning in striatum
Correlationspatiotemporal association by striatal neurons
ConvergenceStriatum receives information from multiple areas
Code a set of tasks into “chunks”
Recall the following
information from the OCD reading:
OCD and the striatum
Abnormal activity in OCD patients
Changes in abnormal activity with treatment
OCD symptoms: sequential repetitive behaviors driven by
compulsions
Behaviors are performed as “chunks”
Graybiel, A. (1998)
Lesion before training
Stopped after 2ndstep!
Prevented the chunking
Lesion after training
Continued with the 3
steps
Bound the behaviors
into a chunk
Training: Two
monkeys trained in 3‐step task
Reward always came at end.
Post surgery: the reward was given one step earlier
unilateral lesion of the nigrostriatal systemGraybiel, A. (1998)
It was a
habit!